An antenna is an apparatus used to transmit or receive an electromagnetic wave signal in a radio equipment. In recent years, design and performance of an antenna of a mobile terminal used for wireless communications increasingly affect a development direction of mobile communications, and especially, greatly affect a wireless terminal such as a mobile phone, a personal digital assistant, or a Moving Picture Expert Group 3 or 4 (MP3/MP4) player. In the design of an antenna, a bandwidth characteristic significantly affects a radiation characteristic. Signal propagation and energy radiation are implemented, based on resonance of frequencies, by an antenna. If one antenna can be resonant at multiple frequencies, the antenna can work at the multiple frequencies. In another aspect, if an antenna has multiple resonance frequencies, a designer and a user may adjust a frequency and a bandwidth as required. If the antenna can work at multiple frequencies, the antenna is called a multimode broadband antenna.
During the implementation of the present invention, the inventor finds that an existing antenna that is most commonly used is a planar inverted F antenna (PIFA) antenna, and a working bandwidth of the PIFA antenna is proportional to a height of the PIFA antenna. If the working bandwidth of the PIFA antenna needs to be broadened to make the PIFA antenna become a multimode broadband antenna, the height of the PIFA antenna needs to be increased, which inevitably affects a thickness of a wireless terminal such as a mobile phone. As a result, a requirement for a thin structure of a wireless terminal such as a mobile phone cannot be met.